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Durable e-textiles based on nanosoldered carbon nanotubes

By Alice Davies 31 May 2018

The incorporation of electronic functions into general textiles is desirable for providing a range of benefits to the user such as health monitoring, advanced functionality and wearable displays among others.

Carbon nanotube-based e-textiles have shown great promise in this field but, due to the nonpolar nature of carbon nanotubes, their adsorption to textile fibres is usually weak thus durability and washability are typically poor. Additionally, the detachment of carbon nanotubes from fabrics has been linked with a number of health problems.

In this product innovation profile, WTiN is reporting on a development from researchers at the National University of Singapore who have demonstrated an ultrasonic nanosoldering method which embeds the carbon nanotubes into the polymer surface thus removing the risk of detachment and providing a safe, durable conductive fabric with potential for application in e-textiles.

Purpose

Development of electronic textiles by incorporating carbon nanotubes into nonwoven fabrics. Demonstration of novel ultrasonic nanosoldering method to provide the required durability and washability, and to overcome the safety concerns associated with detachment of carbon nanotubes from fabrics.

Approach

Researchers at the National University of Singapore have demonstrated a method of nanosoldering carbon nanotubes to nonwoven fabrics by ultrasonication. The resultant material is conductive and thus has potential for application in electronic textiles.

Nonwoven fabrics were treated in a dispersion of carbon nanotubes under ultrasonic radiation. Under these conditions, bubbles form, grow and eventually collapse in the liquid. The collapsing bubbles produce huge pressure which can force dispersed carbon nanotubes onto and into the polymer surface. Close to the polymer surface, the collapsing bubbles can create local temperatures high enough to soften the polymer which further facilitates embedding of the carbon nanotubes into the polymer surface. The result is that carbon nanotubes are firmly rooted onto the polymer surface, making them highly durable and resistant to washing. The carbon nanotubes can form networks which make the nonwoven fabric conductive, with high sensitivity to both strain and pressure.

Results

Attachment of the carbon nanotubes at the surface of the nonwoven fibres was confirmed by SEM, and they were found to remain firmly attached there even after vigorous mechanical stirring for 40 hours in water (equivalent to 80 conventional wash cycles). The carbon nanotubes also appeared to slightly reinforce the nonwoven fabrics, providing comparable tensile strain and improved tensile strength and Young’s modulus. The treated fabrics exhibited electrical conductivity which was sensitive to strain and pressure. The conductance increased at small strains (maximum value at 7% strain) due to increased alignment and reduced proximity between fibres compared to the relaxed state, however as the strain increases, the density of fibres on the same plane decreases thus the conductivity also decreases. The researchers demonstrated the potential of the treated fabrics as sensors for health monitoring; the fabrics exhibited clear and repeatable changes in conductance in response to pulse and respiration when attached to a human wrist and chest respectively.

Impact

The ultrasonic nanosoldering method described in this research embeds carbon nanotubes into the polymer surface thus producing a durable conductive fabric with potential for application in
e-textiles. The response of the fabric to changes in strain and pressure demonstrates its potential for health monitoring applications. The nanosoldering method is compatible with thermoplastic polymers and could therefore be applied to a range of commodity synthetic textile fibres.

Reference: Du, et al., ‘Highly washable e-textile prepared by ultrasonic nanosoldering of carbon nanotubes onto polymer fibers’, Journal of Materials Chemistry C, 2018. DOI: 10.1039/c7tc05179d

Copyright © 2018 The Royal Society of Chemistry

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